PORTLAND — The winter’s warm air temperatures have helped drive up water temperatures in the Gulf of Maine, in line with a continuing trend, and the warm waters could result in lobsters molting their shells earlier than usual and ocean algae blooming ahead of schedule.
In the long run are questions around how rising ocean temperatures might affect the growth and reproduction cycles and distribution of fish and shellfish, whales, zooplankton and other marine life throughout the gulf.
Temperature affects all life processes, but it’s too soon to say if changes brought on by rising water temperatures will be good or bad, said Jeffrey Runge, a biological oceanographer at the University of Maine and a researcher at the Gulf of Maine Research Institute in Portland.
“Higher temperature means higher growth rates, but it also means they require more food in order to attain those higher growth rates,” he said. “But whether there’ll be more food around, I don’t know.”
Gulf of Maine water temperatures have been rising gradually since at least the 1870s, with ups and downs along the way. But the increase has been pronounced in the past decade or so, in the general range of 2 to 5 degrees depending on the ocean depth, Runge said.
The temperature rise in recent years is similar to the 1950s, when the Gulf of Maine warmed up rapidly before falling later, Runge said today in a phone interview from Spain, where he was attending a marine science meeting.
“The question now is whether this is something similar to that warm period in the ’50s, or if this is something different, because we have other forces, we have more (carbon dioxide) being put in the air than 50 or 60 years ago,” he said. “You can’t say what happened in the ’50s will happen now, that it’ll go down. That’s not so clear. Who knows?”
For lobsters, the warmer temperatures could mean they molt their shells and make their annual trek from offshore to nearshore waters earlier in the year. Shrimp could hatch their eggs earlier in the winter. In time, cod and other fish could migrate to the eastern part of the gulf — or out of the gulf altogether — in search of colder waters.
If the waters keep heating up, some scientists speculate that a plankton species, Calanus finmarchicus, that is a key prey for herring, mackerel, right whales and other forage species, could diminish or even disappear from the Gulf of Maine.
And there are questions on ripple effects. For instance, warm water could result in shrimp eggs hatching earlier than in the past. But the hatching dates could come before the phytoplankton bloom that shrimp larvae feed upon.
“These are all angles that you’d need to look into to determine what the effects are going to be,” said Dave Townsend, an oceanographer at the University of Maine.
Air temperatures in Portland have been well above normal for seven consecutive months, and last week’s regional warm spell shattered temperature records across the state for days in a row. Those warm temperatures can also be found in the ocean.
Last Friday, at the tail end of a warm streak, the surface water at a buoy in Casco Bay near Portland came in at 45.5 degrees, or roughly 6 to 10 degrees higher than the same date in any of the past 10 years. At another buoy in Penobscot Bay, off the state’s midcoast, the water temperature was 3 to 9 degrees warmer than readings in the past decade.
The Northeastern Regional Association of Coastal and Observing Systems monitors a series of buoys throughout the Gulf of Maine, which stretches from Cape Cod to Nova Scotia. The association collects data on water and air temperatures, wind speed and direction, wave height, and salinity levels.
Water temperatures have been increasing in recent years at all buoys and at all water depths, said Ru Morrison, executive director of NERACOOS, based in Rye, N.H.
“It’s warming everywhere, at slightly different rates,” he said.